Seismic hazard assessment of eastern Nepal using 1934 and 1988 earthquakes (original) (raw)

Probabilistic Seismic hazard Analysis of Kathmandu City, Nepal

2014

ABSTRACT-Kathmandu is classified as a highly earthquake prone city of Nepal. The center of Kathmandu City is located in the vicinity of ten independent seismic source zones which in reality are active faults. This creates uncertainties in the size, location and the rate of recurrence of earthquakes. Probabilistic seismic hazard analysis provides a framework in which these uncertainties can be identified, quantified and combined in a rational manner to provide a more complete picture of the seismic hazard. This study presents a PSHA of the center of Kathmandu city using the attenuation relationship given by Cornell et al (1979) in order to determine various levels of earthquake-caused ground motion that will be exceeded in a given future time period.

Probabilistic Seismic Hazard Analysis of Nepal

2017

Probabilistic seismic hazard assessment of Nepal has been updated. Nepal has been divided into four area sources based upon density of historical earthquakes. At each sources, earthquake data has been collected from various sources. All data has been converted to moment magnitude, aftershocks and repeated events have been removed, and completeness analysis has been performed. Magnitude-frequency relationship has been developed. Entire area of Nepal has been divided into 1.2*0.6 degrees grid size. Earthquake densities are calculated based upon historical earthquakes using kernel estimation method which accounts the significance of both numbers of earthquakes and size. Considering various attenuation laws developed for subduction zone, peak ground acceleration and spectral acceleration for return period 475 years are calculated at 64 sites.

Probabilistic Seismic Hazard Analysis of Kathmandu City

Kathmandu is classified as a highly earthquake prone city of Nepal. The center of Kathmandu City is located in the vicinity of ten independent seismic source zones which in reality are active faults. This creates uncertainties in the size, location and the rate of recurrence of earthquakes. Probabilistic seismic hazard analysis provides a framework in which these uncertainties can be identified, quantified and combined in a rational manner to provide a more complete picture of the seismic hazard. This study presents a PSHA of the center of Kathmandu city using the attenuation relationship given by Cornell et al (1979) in order to determine various levels of earthquake-caused ground motion that will be exceeded in a given future time period.

Seismic risk assessment and hazard mapping in Nepal

Natural Hazards, 2015

Seismic risk in the form of impending disaster has been seen from past records that moderate-to-large earthquakes have caused the loss of life and property in all parts of Nepal. Despite the availability of new data, and methodological improvements, the available seismic hazard map of Nepal is about two decades old. So an updated seismic hazard model at the country level is imperative and logical. The seismic hazard and risk model constitute important tools for framing public policies toward land-use planning, building regulations, insurance, and emergency preparedness. In fact, the reliable estimation of seismic hazard and risk eventually minimizes social and economic disruption caused by earthquakes. In this frame of reference, the seismic risk assessment at a country level is elementary in reducing potential losses stemming from future earthquakes. Thus, this study investigates structural vulnerability, seismic risk, and the resulting possible economic losses owing to future earthquakes in Nepal. To this end, seismic risk assessment in Nepal is done using an existing probabilistic seismic hazard, a newly developed structural vulnerability, and recently released exposure data. The OpenQuake-engine, the open-source platform for seismic hazard and risk assessment from the Global Earthquake Model initiative, was used to calculate the seismic hazard and risk in Nepal. The seismic hazard and mean economic loss map were formulated for the 1, 2, 5, and 10 % probability of exceedance in 50 years. Finally, the distribution of building damage and corresponding economic losses due to the recurrence of the historical 1934 earthquake was presented in this study.

An Assessment of Earthquake Risk in Thecho of Kathmandu Valley Nepal: Scenario and Reality

2018

Natural disaster cannot be stopped but its effect can be minimized or avoided by adopting technology and necessary human adjustment. Earthquake is a natural event which occurs without early warning signs. Computer based earthquake scenarios are used worldwide to describe and estimate the damage from potential earthquakes. The current study is an attempt to explore potential risk with respect to physical infrastructure and assess modeled and actual physical damage and human loss caused by different earthquake scenario and actual 2015 earthquake event in Thecho of Kathmandu valley. The earthquake scenario is based on two nearest fault lines. Risk Assessment Tools for the Diagnosis of Urban Seismic Risk (RADIUS) method has been applied for estimation of potential building damage and casualties..The research has adopted integrated approach using secondary and primary data sources such as field observation, key informant survey and building survey through purposive random sampling.The st...

Probabilistic seismic hazard assessment for Nepal

Risk Analysis VII, 2010

Written history of great earthquakes in excess of magnitude M8 and recently identified 92 small faults around underlying big three fault systems parallel to the Himalayas show a high seismicity in Nepal. However, since faults are so closed that it is difficult to judge which earthquake belongs to which fault and even some of the faults do not hold earthquakes, the usual method of assigning the earthquakes to the nearest fault developing magnitude-frequency relationship is not applicable. Thus, an attempt has been made here to address the problem considering area sources with different densities at each location based upon historical earthquakes and faults which is real evidence of the seismicity of the region. Separate earthquake densities are calculated based upon historical earthquakes and maximum magnitudes of faults using the kernel estimation method which accounts the significance of both the number of earthquakes and size. Since there is no specific attenuation laws developed for the Himalayan region, five attenuation laws developed for seduction zone are selected and used, giving equal weight to all to minimize the uncertainties. Then, the probabilistic spectra for various return periods are calculated, compared with previous estimates and various aspects discussed.

Integrated Seismic Risk Assessment in Nepal

2022

As Nepal is at high risk of earthquakes, the district-wide (VDC/Municipality level) study has been performed for vulnerability assessment of seismic-hazard, and the hazard-risk study is incorporated with social conditions as it has become a crucial issue in recent years. There is an interrelationship between hazards, physical risk, and the social characteristics of populations which are significant for policy-makers and individuals. Mapping the spatial variability of average annual loss (seismic risk) and social vulnerability discretely does not reflect the true nature of parameters contributing to the earthquake risk, so when the integrated risk is mapped, such combined spatial distribution becomes more evident. The purpose of this paper is to compute the risk analysis from exposure model of the country using OpenQuake and then integrate the results with socioeconomic parameters. The methodology of seismic-risk assessment and the way of combining the results of the physical risk and socioeconomic data to develop integrated vulnerability score of the regions has been described. This study considers all 75 districts and corresponding VDC/Municipalities using the available census. The combined vulnerability score has been developed and presented by integrating earthquake risk and social vulnerability aspect of the country and represented in form of map produced using ArcGIS 10. The knowledge and information of the relationship between earthquake hazard and the demographic characteristics of population in the vulnerable area is imperative to mitigate the local impact from earthquakes. Therefore, we utilize social vulnerability study as part of a comprehensive risk management framework to recuperate and recover from natural disasters.

Probabilistic seismic hazard assessment of NW and central Himalayas and the adjoining region

Journal of Earth System Science, 2015

The Himalayan region has undergone significant development and to ensure safe and secure progress in such a seismically vulnerable region there is a need for hazard assessment. For seismic hazard assessment, it is important to assess the quality, consistency, and homogeneity of the seismicity data collected from different sources. In the present study, an improved magnitude conversion technique has been used to convert different magnitude scales to moment magnitude scale. The study area and its adjoining region have been divided into 22 seismogenic zones based upon the geology, tectonics, and seismicity including source mechanism relevant to the region. Region specific attenuation equations have been used for seismic hazard assessment. Standard procedure for PSHA has been adopted for this study and peak ground motion is estimated for 10% and 2% probability of exceedance in 50 years at the bed rock level. For the 10% and 2% probability of exceedance in 50 years, the PGA values vary from 0.06 to 0.36 g and 0.11 to 0.65 g, respectively considering varying b-value. Higher PGA values are observed in the southeast part region situated around Kaurik Fault System (KFS) and western parts of Nepal. Management Authority (NDMA 2011), Government of India, presented various probabilistic seismic

State of Seismic Hazard Analysis: Reviewing the Needs after Mw 7.8 Gorkha, Nepal Earthquake

Journal of Development Innovations, 2020

Although Nepal experienced Mw 7.8 earthquake in 2015, researchers are arguing that a high magnitude earthquake approaching Mw 9 is likely to occur again in the future. This finding is based on the geodetically measured elastic strain stored at a rate of about 20 mm/year on the Main Himalayan Thrust (MHT) for the last ~>700 years, and also on the findings of paleo seismological studies conducted at some parts of the Terai-Siwalik region of Nepal. Based on literature reviews, this paper provides an overview of geological settings followed by the status of earthquake hazard assessment in Nepal. For better understanding of seismic hazard in community level, “further research needs are identified". It includes, among others, the need of analyzing seismic hazard based on the peak ground velocity (PGV) particularly for those locations which are underlain by thick sediments, and where the trend of high-rise building constructions are also increasing.

Probabilistic Seismic Hazard Analysis of Nepal considering Uniform Density Model

2017

Probabilistic seismic hazard analysis for Nepal has been carried out in terms of peak ground acceleration. A detailed earthquake catalogue within the rectangular area bounded by the coordinates (N253000,E783000), (N313000,E893000)from 1255 up to 2015 A.D and new seismic and seismo tectonic map have been prepared. Five hundred twenty eight numbers of areal sources has been proposed and historical earthquakes are plotted in the map of Nepal for identifying and characterizing the seismic sources. The completeness of the data has been checked by using Stepp’s procedure. Seismicity in four regions of study area has evaluated by defining ’a’ and ’b’ parameters of Gutenberg Richter recurrence relationship. The uniform density model has been adopted to get the hazard in terms of contour map for peak ground acceleration for hard, medium and soft subsoil conditions for different probability of exceedence in 50 years period. The average seismic hazard curve for Nepal for hard, medium and soft ...